MICROCHEMICAL REACTIONS OF COPPER 385 
elements analogous to arsenic as shown by their position in 
the Periodic System. We find, for example, crystalline salts 
of silver with phosphorus, as silver phosphate; with antimony, 
silver antimonate; with vanadium, silver vanadates; with chro¬ 
mium, silver chromates; with molybdenum, silver molybdates. 
Of these salts the chromates and vanadates can be employed for 
the detection of silver, but the phosphates, antimonates and 
molybdates cannot be made to yield sufficiently characteristic 
results. 
EXPERIMENTS. 
a. Test a neutral solution of AgNOs in the manner suggested above. 
b. Recrystallize a preparation of Ag3As04 from HNO3. 
c. Try another preparation with NH4OH. 
d. Test a mixture of Ag and Pb. Then one of Ag and Hg. 
e. Try the above reaction on salts of Ca, Sr and Ba, first alone, then in mix¬ 
tures but with no Ag present. 
/. Try salts of Mg, Zn and Cd. 
g. Try a salt of Ca in the presence of much NH4CI. 
COPPER. 
Crystal Forms and Optical Properties of Common Salts of 
Copper. 
A. / 50 rR 0 P/C. — Cuprous chloride, bromide and 
iodide. 
B. ANISOTROPIC. 
Hexagonal. 
Tetragonal. —Ammonium-copper chloride; potas¬ 
sium-copper chloride. 
Orthorhombic. — Chloride; sulphate plus 4 NH3. 
Monoclinic. — Acetate; potassium-copper sul¬ 
phate. 
Triclinic. — Sulphate. 
DETECTION. 
A. By Means of Potassium Mercuric Thiocyanate. 
The reagent is applied by Method I, page 299, to neutral or 
weakly acid solutions; it must be neither alkaline nor ammoniacal. 
The appearance, properties and peculiarities of copper mercuric 
